diff --git a/cabal2nix.cabal b/cabal2nix.cabal
--- a/cabal2nix.cabal
+++ b/cabal2nix.cabal
@@ -1,5 +1,5 @@
 name:           cabal2nix
-version:        2.9.1
+version:        2.9.2
 synopsis:       Convert Cabal files into Nix build instructions.
 category:       Distribution, Nix
 stability:      stable
@@ -72,7 +72,7 @@
 maintainer:     Peter Simons <simons@cryp.to>
 license:        BSD3
 license-file:   LICENSE
-tested-with:    GHC == 8.2.2
+tested-with:    GHC == 8.2.2, GHC == 8.4.1
 build-type:     Simple
 cabal-version:  1.24
 
diff --git a/src/Cabal2nix.hs b/src/Cabal2nix.hs
--- a/src/Cabal2nix.hs
+++ b/src/Cabal2nix.hs
@@ -102,7 +102,8 @@
 parsePlatform :: P.ReadP r Platform
 parsePlatform = do arch <- P.choice [P.string "i686" >> return I386, P.string "x86_64" >> return X86_64]
                    _ <- P.char '-'
-                   os <- P.choice [P.string "linux" >> return Linux, P.string "darwin" >> return OSX]
+                   os <- P.choice [ P.string "linux" >> return Linux, P.string "darwin" >> return OSX
+                                  , P.string "windows" >> return Windows]
                    return (Platform arch os)
 
 pinfo :: ParserInfo Options
diff --git a/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs b/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs
--- a/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs
+++ b/src/Distribution/Nixpkgs/Haskell/PackageSourceSpec.hs
@@ -2,13 +2,12 @@
   ( Package(..), getPackage, getPackage', loadHackageDB, sourceFromHackage
   ) where
 
-import Control.DeepSeq (force)
 import qualified Control.Exception as Exception
 import Control.Monad
 import Control.Monad.IO.Class
 import Control.Monad.Trans.Maybe
 import Data.Bifunctor
-import qualified Data.ByteString.Char8 as BS -- TODO: Deal with utf-8 encoding!!
+import qualified Data.ByteString.Char8 as BS
 import Data.List ( isSuffixOf, isPrefixOf )
 import qualified Data.Map as DB
 import Data.Maybe
@@ -25,11 +24,13 @@
 import Distribution.Version
 import qualified Hpack.Config as Hpack
 import qualified Hpack.Render as Hpack
-import OpenSSL.Digest ( digestString, digestByName )
+import OpenSSL.Digest ( digest, digestByName )
 import System.Directory ( doesDirectoryExist, doesFileExist, createDirectoryIfMissing, getHomeDirectory, getDirectoryContents )
 import System.Exit ( exitFailure )
 import System.FilePath ( (</>), (<.>) )
 import System.IO
+import qualified Data.Text as T
+import qualified Data.Text.Encoding as T
 
 data Package = Package
   { pkgSource   :: DerivationSource
@@ -193,18 +194,21 @@
 handleIO :: (Exception.IOException -> IO a) -> IO a -> IO a
 handleIO = Exception.handle
 
+encodeUtf8 :: String -> BS.ByteString
+encodeUtf8 = T.encodeUtf8 . T.pack
+
 hpackDirectory :: FilePath -> MaybeT IO (Bool, Cabal.GenericPackageDescription)
 hpackDirectory dir = do
   mPackage <- liftIO $ Hpack.readPackageConfig Hpack.defaultDecodeOptions {Hpack.decodeOptionsTarget = dir </> Hpack.packageConfig}
   case mPackage of
     Left err -> liftIO $ hPutStrLn stderr ("*** hpack error: " ++ show err ++ ". Exiting.") >> exitFailure
     Right (Hpack.DecodeResult pkg' _ _) -> do
-      let hpackOutput = Hpack.renderPackage [] pkg'
-          hash = printSHA256 $ digestString (digestByName "sha256") hpackOutput
-      case runParseGenericPackageDescription "<hpack output>" (BS.pack hpackOutput) of
+      let hpackOutput = encodeUtf8 $ Hpack.renderPackage [] pkg'
+          hash = printSHA256 $ digest (digestByName "sha256") hpackOutput
+      case runParseGenericPackageDescription "<hpack output>" hpackOutput of
         Left msg -> liftIO $ do
           hPutStrLn stderr "*** hpack output:"
-          hPutStrLn stderr hpackOutput
+          BS.hPutStrLn stderr hpackOutput
           hPutStrLn stderr "*** cannot parse hpack output:"
           hPutStrLn stderr msg
           fail "*** Exiting."
@@ -216,11 +220,9 @@
   -- that do not represent valid characters. To catch that exception, we need to
   -- wrap the whole block in `catchIO`.
   MaybeT $ handleIO (\err -> Nothing <$ hPutStrLn stderr ("*** parsing cabal file: " ++ show err)) $ do
-    buf <- withFile file ReadMode $ \ h -> do
-      hSetEncoding h utf8
-      hGetContents h >>= Exception.evaluate . force
-    let hash = printSHA256 (digestString (digestByName "sha256") buf)
-    case runParseGenericPackageDescription file (BS.pack buf) of
+    buf <- BS.readFile file
+    let hash = printSHA256 (digest (digestByName "sha256") buf)
+    case runParseGenericPackageDescription file buf of
       Left msg | failHard -> liftIO $ do
           hPutStrLn stderr $ "*** cannot parse " ++ show file ++ ":"
           hPutStrLn stderr msg